subject: Automatic Vertical Storage And Retrieval System [print this page] Extractors of automatic storage and retrieval system typically travel vertically along and between the storage arrays by means of a chain or cable system driven by an electric motor. Optical encoders or similar means are used in automatic storage and retrieval system to position the extractor along the vertical array. An automatic vertical storage and retrieval system which uses an optical encoder at the motor to position the extractor must be periodically calibrated to account for drift in the calibration. The chain or cable drive system operates not only to drive and position the extractor mechanism but also to support the extractor mechanism while retrieving stored items or presenting retrieved items to the operator. This invention pertains to an automatic storage and retrieval system and, more particularly, to a system having an extractor mechanism which is vertically stable and insensitive to changes in loading by means of one or more locking dogs.
The chain or cable drive system in a typical automatic storage and retrieval system may consist of a pair of chains or cables. One end of the each chain or cable is attached to opposite sides of the extractor, and the other end of each chain or cable is provided with a counterweight. The counterweight is used to compensate for the weight of the payload and to ease the strain on the motor drive during vertical displacement of the extractor. However, the extractor is vertically displaced in both a laden and an unladen condition and each payload differs in weight. Therefor, the effectiveness of counterweights in known automatic storage and retrieval system is limited. A payload weight of 500 pounds or more is not untypical in automatic vertical storage and retrieval systems. Because of the weight of such payloads, a danger of chain or cable breakage exists in known vertical storage and retrieval systems. Even if the chain or cable does not break, any stretching of the chain, cable or support members, even if slight, could cause a misalignment problem.
